Yeast count with a microscope
Claude Jolicoeur
I recently graduated to using a microscope to count the yeast population prior to bottling, thus permitting an even better control of bottle conditioning...
And this seems to have raised some interest and questions... Hence here are a few details.
Picture of my setup:
The microscope is a Cenco, which dates from the 70's or 80's. There is nothing fancy about it, it is a model which I believe was quite popular for school labs at the time. It has 3 objectives, 4x, 10x and 40x and a 10x eyepiece which gives overall magnifications of 40, 100 and 400x. Cenco is/was an american company, but the microscope is made in Japan.
I don't really use the eyepiece as I prefer to use my camera - much easier for the eyes. You need a SLR for this, where it is possible to take the lens out and replace it by an adaptor that fits in place of the eyepiece.
The adaptor is this one:
Note there exist more expensive adaptors that provide magnification. I don't have that and don't see this as necessary. I can easily get extra magnification from the camera resolution (18 megapixels...)
Then I can connect the camera to the computer via USB, and Canon provides a nice software called EOS Utilities that permits to control the camera in live view, check the focus on the display, and take pictures. Works very nicely. I would guess other camera manufacturers like Nikon would provide equivalent functionalities.
Another acessory needed is a counting chamber, also called hemacytometer or Neubauer chamber (https://en.wikipedia.org/wiki/Hemocytometer), which is a special plate that contains a known volume of cider, and has a grid, thus permitting to count the number of cells. You can pay as little as 15$ or over 200$ for one of these. I got a cheaper one... and I don't know what a more expensive one would have as advantage (probably better precision).
See for example
When you shop for a microscope, there are a few things you should be looking for:
- mechanical stage - this permits very small and controlled movements of the plate, essential and without this you'd have to move the plate with your hands and there is no way you would succeed in counting.
- good light system, with focusing and an aperture control which permits increasing the contrasts to see the grid.
- a "2 speed" focusing system - i.e. rough and fine focus.
Here is an example of an entry-level "made in China" microscope that provides these features:
Following picture is a counting example. The picture is cropped on a square 1mm x 1mm, which is divided in 16 smaller squares, and the thickness is 0.1 mm, hence a known volume of 0.1 mm³. You can count about 80 cells inside this volume, which makes a population of 800 000 cells per mL. This was taken with the 10x objective. Note the cells are somewhat out of focus - it is not generally possible to have the cells and the grid lines in the same focus - it is a bit tricky to find the sweet spot where the grid is easily seen and the cells are not too much blurred...
And here is a shot taken with the 40x objective and maximum magnification from the camera. The blus color is methylene blue, a dye that permits to identify the dead cells.
Miguel Pereda
Miguel A. Pereda
CiderSupply.com
C.